Why does everyone have different blood types?

More than a century after the discovery of blood types, people still don’t really know what our bodies divide into different blood types for? And does having such blood types really matter?

The scientific website Mosaic has published an article about blood types by reporter Carl Zimmer to help us understand more about the science of blood types.

1. When my parents informed me that my blood type is A, I felt a strange sense of pride. If A+ is the best grade in school, surely A is also the best blood type.

Why does everyone have different blood types?
40% of white people have blood type A.

But soon I realized how stupid it was to feel that way. But I still don’t know much about what blood type A really means. When I was an adult, all I knew was that if I had to be hospitalized and needed a blood transfusion, the doctors would have to know for sure that they needed to give me a blood bag with the right blood type.

The nagging questions are still there. Why do 40% of white people have blood type A, when only 27% of Asians have this blood type? Where do the different blood types come from? And what do they mean? For answers, I met with experts – doctors, geneticists, evolutionary biologists, virologists and nutritional scientists.

In 1900, Austrian doctor Karl Landsteiner was the first to discover blood groups, and won the Nobel Prize in Physiology or Medicine for this research in 1930. Since then scientists have developed many more. Powerful tool to aim to learn about blood groups. They discovered some interesting clues – such as tracing the “ancestor” of blood types and figuring out the effect of blood types on human health. But in many ways, blood types remain a mystery. Scientists have not yet come up with a satisfactory explanation for the existence of blood types.

2. Today, doctors know about blood types, and they can save many lives with blood transfusions. But historically, the idea of giving blood from one person to another was a dream. Renaissance doctors thought about what would happen if they injected blood into a patient’s vein. Some say it could be a cure for all sorts of ailments, even madness. Finally, in the 1600s, some doctors tested the idea, with terrible results. A French doctor injected the blood of a calf into a mentally ill man. This person immediately sweats, vomits, the urine turns gray. After a blood transfusion, he died.

Accidents like these gave blood transfusions a bad reputation for 150 years. Even in the 19th century, only a few doctors dared to administer blood transfusions. One of them was a British doctor named James Blundell. Like other doctors, he has seen many female patients die from bleeding during childbirth. After the death of a patient in 1817, he found it impossible not to experiment with blood transfusions.

I couldn’t take it any longer, the patient’s life could very well have been saved with a blood transfusion ,” he later wrote.

Dr. Blundell believes that previous blood transfusion disasters were caused by a very basic error: the transmission of “animal blood” . Therefore, he concluded that doctors should not mix blood transfusions between species , because ” different blood types vary greatly “.

That is, patients should only receive human blood. But still no one tried to conduct a blood transfusion like that. And Blundell experimented by designing a system of funnels, tubes and syringes that could transfer blood from a donor to a patient. After testing the system on dogs, Blundell was put in a situation where he had to save a patient who was bleeding to death. ” The blood transfusion alone could give him a chance to live ,” he wrote.

And several blood donors provided Blundell with 14 ounces (about 0.4 liters) of blood, which he injected into the patient’s arm. After that, the patient said he felt better – but two days later he died.

Even so, the experience convinced Blundell that blood transfusions would be of great benefit to mankind, and he continued to give blood to many desperate patients for years to come. It is known that he has performed 10 blood transfusions. 4 patients were saved.

3. Blundell was right to believe that humans should only receive human blood. But he didn’t know another important fact about blood: that humans should only receive blood from certain humans . That could be the omission that caused some patients to die. What made all those deaths all the more tragic when the blood type was discovered, a few decades later, was the result of a fairly simple process.

In the late 1800s, when scientists mixed the blood of many people in test tubes, they noticed that sometimes red blood cells stick together. But since this is often the patient’s blood, they consider such clots as well as certain types of pathology unworthy of investigation. No one bothered to examine the blood of healthy people, until Karl Landsteiner wondered what would happen. Immediately, he found that the blood mixture of healthy people sometimes clumped.

Why does everyone have different blood types?
Humans should only receive human blood.

Landsteiner charted blood clots . He took blood samples from everyone in the lab, including his own. Each blood sample is separated into two parts, consisting of red blood cells and plasma, then he mixes one person’s plasma with another’s red blood cells.

Landsteiner discovered that blood only clots if he mixes the blood of certain people together. By testing all the combinations in turn, he eventually sorted his blood types into three groups, alphabetically named A, B, and C. (The blood group C was later renamed O. , and a few years later other researchers discovered group AB.In the mid-20th century, American researcher Philip Levine found another way to classify blood, based on how weak that blood type was. Rh factor or not, if present, it will be denoted Rh+, if not, write Rh-, next to the names of blood groups).

When Landsteiner mixed the blood of different people, he discovered several patterns. If the plasma of a person with blood group A is mixed with the red blood cells of another person who is also group A, the blood will remain liquid, without clots. The same thing happens with the blood of people with type B blood. But if you mix the plasma of people with blood type A with people with blood type B, and vice versa, the blood will clot.

People with blood type O are different. If Landsteiner mixes group A and B blood cells with type O plasma, the blood will clot, but if group A and B plasma is mixed with group O blood cells, the blood will be normal.

It is the clumping that makes blood transfusions potentially dangerous . The clumping interferes with blood circulation and causes the patient to bleed profusely, have difficulty breathing, and possibly die. Landsteiner doesn’t know exactly how to distinguish blood types. Generations of doctors later discovered that the red blood cells in each blood type have different molecules on their surface. In blood type A, for example, cells build molecules in two stages, like two floors of a house. The first layer is called the H antigen. On the surface of this first layer, cells again build a second layer, called the A antigen.

Meanwhile, the blood of group B people builds the second floor of the house in a different shape. And people with type O blood only have a one-story house: that is, the cells only build the H-antigen layer and don’t build any more.

The immune systems of people from the same group will have many similarities. If people are transfused with the wrong blood type, the immune system reacts, as if the foreign blood were an invader. This is an exception for people with type O blood. Type O blood has only the H antigen, and this antigen is present in all other blood groups. Therefore, people with blood type O can donate blood to people with blood type A or B. This similarity makes people with type O blood “precious blood philanthropists”.

Landsteiner’s findings opened the door to a safe haven for blood transfusions, and even today blood banks still use his clotted blood cell test to test blood groups consistently. fast, reliable.

But while Landsteiner answered old questions, he raised new questions. That is, the blood group for what? Why do people have different blood types?

4. In 1996, a naturopath named Peter D’Adamo published the book “Eat Right 4 Your Type”. D’Adamo argues that we must eat according to our color group, in order to harmonize with our evolution.

D’Adamo states that blood types ” seem to have reached the crucial crux of human evolution “. According to D’Adamo, blood type O comes from hunter-gatherer ancestors in Africa, blood type A is at the dawn of agriculture, and blood type B is from 10,000 to 15,000 years ago in the Himalayan highlands. . Blood type AB is a modern mix of blood types A and B.

Why does everyone have different blood types?
Blood type AB is a modern mix of blood types A and B.

From these assumptions, D’Adamo claims that blood type determines what foods we should eat. For example, people with blood type A should be vegetarian. As for the ancient hunters with blood type O, they should have a meat-rich diet and avoid grains and dairy. According to the book, foods that don’t match your blood type contain antigens that can cause all sorts of illnesses. D’Adamo recommends the diet as a way to reduce infections, lose weight, fight cancer and diabetes, and slow the aging process.

D’Adamo’s book has sold 7 million copies and been translated into 60 languages. After D’Adamo’s book, a series of books on blood group matching also appeared. D’Adamo also sells blood type-specific diets on his website. As a result, patients often ask their doctors if the blood type diet really works.

The best way to answer that question is to conduct an experiment. In his book Eat Right 4 Your Type, D’Adamo writes that he conducted a decade-long trial of a blood type diet for women with cancer. However, 18 years later, the data from this trial is still unpublished.

Recently, researchers at the Red Cross in Belgium decided to look at whether there is any evidence of any benefit in the blood type diet. Despite examining more than 1,000 studies, they were all to no avail. ” There is no direct evidence for the health effects of the blood type diet ,” says Emmy De Buck of the Red Cross.

However, some people who follow the diet have had positive results. According to Ahmed El-Sohemy, a nutrition scientist at the University of Toronto, that’s not a reason to think that the blood type diet is successful.

El-Sohemy is an emerging expert in the field of nutrigenomics – the combination of nutrition and genes. He and his colleagues studied 1,500 people. As a scientist, he realized that Eat Right 4 Your Type was not scientific at all.

5. After Landsteiner discovered human blood types in 1900, scientists wondered if other animals had such blood types. It seems that some primates have mixed blood with human blood types. But for a long time, people did not know what the discovery was for. The fact that a monkey’s blood does not clot with type A blood does not mean that the monkey has inherited the same type of A blood gene.

Beginning in the 1990s, scientists deciphered the molecular biology of blood types. They discovered that a single gene, called ABO, was responsible for building the second floor of the blood type house. The A version of the gene has several important mutations that are different from the B gene. People with type O blood have mutations in the ABO gene that prevent them from making the enzyme that builds A or B antigens.

The scientists were then able to start comparing the ABO genes of humans with those of other animals. Laure Ségurel and colleagues at the National Center for Scientific Research in Paris have led an ambitious study of the ABO gene in primates. And they found that human blood types are actually very ancient in origin. Apes and humans both have variants of both A and B blood types, and those variants come from a common ancestor, which lived 20 million years ago. Even human blood groups have an even older origin, it is difficult to know the age.

6. The most powerful demonstration of humanity’s ignorance of the benefits of blood types came to light in 1952 in Bombay. Doctors discovered that there were a small number of patients who did not have ABO blood type – that is, no A, no B, no AB, no O. If blood types A and B are a two-story house, and blood type O is the house. In a one-story house, the blood of Bombay patients was only “a vacant lot”.

The “Bombay phenotype” is present in some other people, but very rarely. And as far as scientists say, it doesn’t do any harm. Its only risk is when a blood transfusion is needed. People with the Bombay phenotype can only receive blood from people who are in the same situation as them. Even blood type O, arguably the most universal blood type, they were not accepted.

Some scientists think the explanation for blood types may lie in blood variations. That’s because different blood types can protect us from different diseases.

The first time doctors recognized a link between blood types and various diseases was in the mid-20th century. ” There are still a lot of links between blood types and infections, cancer and some diseases. ” , says Pamela Greenwell of the University of Westminster. For example, people with blood type A have a higher risk of certain types of cancer, such as pancreatic and blood cancers; are also prone to chickenpox, heart attack and malaria. On the other hand, people with blood type O can develop ulcers. According to the study, this is because immune cells, such as those of people with type O blood, are better able to recognize infectious cells than other blood types.

What’s more confusing lies in the link between blood types and diseases that have nothing to do with blood. For example norovirus (Norovirus is a group of viruses that cause diarrhea, vomiting and abdominal pain. Norovirus is often called by other names such as gastroenteritis virus, gastritis and food poisoning). Norovirus spreads like a cruise ship, it sweeps through hundreds of passengers, causing violent vomiting and diarrhea. It invades cells in the intestines, causing blood cells to be affected. However, blood type does affect the risk that they will be infected by a particular strain of norovirus.

The answer to this mystery may lie in the fact that blood cells are not the only cells that produce blood group antigens. These antigens are also produced by cells in the walls of blood vessels, the respiratory tract, skin, and hair. Many people even secrete blood group antigens in their saliva. Norovirus makes us sick by penetrating blood type antigens produced by cells in the gut.

However, norovirus can only penetrate a cell if its proteins closely match the antigen of the blood type. Therefore, it is possible that each norovirus strain has proteins that match certain blood type antibodies. That’s why blood type can affect the type of norovirus that makes us sick.

This could be a clue as to why a blood type has been traced back millions of years. Our primate ancestors were in constant battle with a multitude of pathogens, including viruses, bacteria, and other enemies. Some pathogens may have adapted and know how to exploit different types of blood group antigens.

Finally, the author of the article on science site Mosaicscience.com said that the story of blood type intrigued him since he was a boy, and as he grew older, he realized: “Ultimately, reason Since I have blood type A, it doesn’t matter!” It’s just that my parents gave birth to me like that….